/*
 * @Description:
 * @Date: 2021-12-30 14:10:17
 * @LastEditTime: 2021-12-30 21:55:49
 */
(function (win, lib) {
  var doc = win.document

  var docEl = doc.documentElement

  var metaEl = doc.querySelector('meta[name="viewport"]')

  var flexibleEl = doc.querySelector('meta[name="flexible"]')

  var dpr = 0

  var scale = 0

  var tid

  var flexible = lib.flexible || (lib.flexible = {})

  if (metaEl) {
    console.warn('将根据已有的meta标签来设置缩放比例')

    var match = metaEl.getAttribute('content').match(/initial\-scale=([\d\.]+)/)

    if (match) {
      scale = parseFloat(match[1])

      dpr = parseInt(1 / scale)
    }
  } else if (flexibleEl) {
    var content = flexibleEl.getAttribute('content')

    if (content) {
      var initialDpr = content.match(/initial\-dpr=([\d\.]+)/)

      var maximumDpr = content.match(/maximum\-dpr=([\d\.]+)/)

      if (initialDpr) {
        dpr = parseFloat(initialDpr[1])

        scale = parseFloat((1 / dpr).toFixed(2))
      }

      if (maximumDpr) {
        dpr = parseFloat(maximumDpr[1])

        scale = parseFloat((1 / dpr).toFixed(2))
      }
    }
  }

  if (!dpr && !scale) {
    var isAndroid = win.navigator.appVersion.match(/android/gi)

    var isIPhone = win.navigator.appVersion.match(/iphone/gi)

    var devicePixelRatio = win.devicePixelRatio

    if (isIPhone) {
      // iOS下，对于2和3的屏，用2倍的方案，其余的用1倍方案

      if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {
        dpr = 3
      } else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)) {
        dpr = 2
      } else {
        dpr = 1
      }
    } else {
      // 其他设备下，仍旧使用1倍的方案

      dpr = 1
    }

    scale = 1 / dpr
  }

  docEl.setAttribute('data-dpr', dpr)

  if (!metaEl) {
    metaEl = doc.createElement('meta')

    metaEl.setAttribute('name', 'viewport')

    metaEl.setAttribute(

      'content',

      'initial-scale=' +

scale +

', maximum-scale=' +

scale +

', minimum-scale=' +

scale +

', user-scalable=no'

    )

    if (docEl.firstElementChild) {
      docEl.firstElementChild.appendChild(metaEl)
    } else {
      var wrap = doc.createElement('div')

      wrap.appendChild(metaEl)

      doc.write(wrap.innerHTML)
    }
  }

  function refreshRem () {
    var width = docEl.getBoundingClientRect().width

    if (width / dpr > 540) {
      width = width * dpr
    }

    var rem = width / 10

    docEl.style.fontSize = rem + 'px'

    flexible.rem = win.rem = rem
  }

  win.addEventListener(

    'resize',

    function () {
      clearTimeout(tid)

      tid = setTimeout(refreshRem, 300)
    },

    false

  )

  win.addEventListener(

    'pageshow',

    function (e) {
      if (e.persisted) {
        clearTimeout(tid)

        tid = setTimeout(refreshRem, 300)
      }
    },

    false

  )

  if (doc.readyState === 'complete') {
    doc.body.style.fontSize = 12 * dpr + 'px'
  } else {
    doc.addEventListener(

      'DOMContentLoaded',

      function (e) {
        doc.body.style.fontSize = 12 * dpr + 'px'
      },

      false

    )
  }

  refreshRem()

  flexible.dpr = win.dpr = dpr

  flexible.refreshRem = refreshRem

  flexible.rem2px = function (d) {
    var val = parseFloat(d) * this.rem

    if (typeof d === 'string' && d.match(/rem$/)) {
      val += 'px'
    }

    return val
  }

  flexible.px2rem = function (d) {
    var val = parseFloat(d) / this.rem

    if (typeof d === 'string' && d.match(/px$/)) {
      val += 'rem'
    }

    return val
  }
})(window, window.lib || (window.lib = {}))
